This invention relates to engine fuel injectors and, more particularly, to a solenoid actuated fuel injector having a magnetic coil body with upper and lower members assembled with an unwelded telescoped joint.
It is well known in the automotive engine art to provide solenoid actuated fuel injectors for controlling the injection of fuel into the cylinders of spark ignition engines, generally through intake manifold runners or intake ports of the cylinders. Generally, such injectors include a body having added internal and external components which are assembled and welded, brazed or otherwise sealed together to provide internal fuel passages for conducting fuel flow. Fuel flow is controlled by a solenoid valve having an orificed valve seat controlled by an armature with a valve element, spring biased toward the seat for closing the valve. A solenoid coil surrounds a magnetic inner pole to which the armature is drawn when the coil is energized to open the valve.
For efficient operation, a magnetic coil body is provided that generally surrounds the coil and provides a magnetic circuit or flux path extending from the magnetic pole around the outside of the coil to the armature and, through the armature, back to the coil. A gap provided in the flux path between the armature and the pole is closed when the armature is drawn to the pole to open the valve. A second gap is provided between the armature and the coil body to allow free motion of the armature. Other gaps in the magnetic flux path are controlled or avoided as they decrease magnetic force on the armature so that a larger coil using greater energy may be required.
The coil body is commonly made in two sections, such as upper and lower coil bodies, which are assembled around the coil and welded together to close the gap in the magnetic flux path. However, this requires assembly steps and equipment which add to the complexity and cost of the assembly process.
The present invention provides an injector having a coil body assembly with modified upper and lower coil body components that are designed to be assembled and held together with a spring type press fit instead of by welding. The components are made with generally tubular end portions that are telescoped together in assembly to provide an enlarged central portion that surrounds the magnetic coil. The downwardly open tubular portion of the upper body is longer and slightly smaller than the upwardly open tubular portion of the lower body, so that the upper portion may be fitted into the lower portion. A longitudinal slot is provided in the upper portion for protrusion of insulated coil terminals. The slot also allows the upper portion to spring in slightly upon insertion into the lower portion. Thus the upper and lower body are retained in assembly by a spring biased press fit of the components. The press fit holds the telescoped portions of the assembly in close contact, providing good path for carrying the magnetic flux of the coil. Welding of the components together is accordingly not required and manufacture is simplified.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.